How to evaluate a triangular fermion loop

  • Context: Graduate 
  • Thread starter Thread starter c++guru
  • Start date Start date
  • Tags Tags
    Fermion Loop
Click For Summary
SUMMARY

This discussion focuses on evaluating a triangular fermion loop in quantum field theory (QFT), specifically involving a scalar field decaying into a fermion-antifermion pair that produces two photons. The process involves tracing back from the photon vertices using vertex factors and propagators. Participants highlight the importance of considering the chiral anomaly, which introduces complexities in the integral evaluation. For comprehensive guidance, consulting advanced QFT textbooks is recommended.

PREREQUISITES
  • Understanding of quantum field theory (QFT) principles
  • Familiarity with fermion-antifermion interactions
  • Knowledge of vertex factors and propagators in particle physics
  • Awareness of the chiral anomaly and its implications
NEXT STEPS
  • Study advanced QFT textbooks for detailed integral evaluation techniques
  • Research the implications of the chiral anomaly in particle interactions
  • Explore the role of photon exchange diagrams in fermion loops
  • Learn about the mathematical techniques for tracing diagrams in QFT
USEFUL FOR

This discussion is beneficial for theoretical physicists, graduate students in particle physics, and researchers focusing on quantum field theory and its applications in particle interactions.

c++guru
Messages
11
Reaction score
0
Say I have a scalar field which decays into to a fermion - anti fermion pair which then interact in a closed loop to produce two photons. How would I evaluate this? Can I just follow the loop backwards from any of the two photon vertices and just write vertex factor, propogator, vertex factor, propogator, vertex factor, propogator, and then take the trace of that?
 
Physics news on Phys.org
Yes. But the evaluation of the integral you get can have tricky subtleties related to the chiral anomaly.
 
I end up with this
Screen%20Shot%202014-10-20%20at%201.18.59%20PM.png

How in the world do I do this integral?
 
I believe you only used one diagram; you have to add the diagram with the two photons exchanged.

See any advanced QFT textbook for how to evaluate the integral.
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
5K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
6K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K